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Model Answers

Case 1

Case 1 Model Answer:

Acute aortic syndrome with intramural haematoma

Findings and interpretation:

Non-contrast CT:

  • There is a rim of hyperdensity around the thoracic aorta, which extends to a lesser degree down to the abdominal aorta. At the descending thoracic aorta, an intimal calcification is visualised between the aortic lumen and hyperdense rim.
  • There is a large outpouching coming off the aortic arch and protruding into the left hemithorax.

Arterial CT:

  • The aortic wall from the arch to the abdominal aorta appears thickened, with greatest thickening noted at the arch and descending thoracic aorta.
  • There are multiple luminal irregularities / protrusions into the aortic wall at the aortic arch which fill with contrast and form part of the lumen. These represent penetrating aortic ulcers.
  • There are surgical clips seen at the proximal abdominal aorta, where an aortic graft has been surgically placed (presumably to manage an abdominal aortic aneurysm). The graft extends to the common iliac arteries.
  • There are bilateral internal iliac aneurysms and atherosclerotic calcifications at that level.

Pertinent negative findings:

  • There is no mediastinal haematoma.
  • No haemothorax.
  • No aortic aneurysm.
  • No intimo-medial dissection flap.


  • Calcifications at the left apex represent granulomas, likely sequelae of old TB
  • Mild emphysematous changes in both lungs
  • Bilateral renal scarring and simple cyst in right kidney.


The findings indicate penetrating atherosclerotic ulcers at the aortic arch of variable size, which have caused haemorrhage into the aortic media / wall.


Principal Diagnosis:

Acute aortic syndrome with aortic ulcers and intramural haematoma.


Differential diagnosis:

Aortic aneurysm / pseudo-aneurysm

Aortic dissection (however, there is no intimal flap).



Urgently contact the referring physician and inform of findings, as this constitutes a surgical emergency (this can rapidly progress to dissection and rupture).

Urgent cardiothoracic surgery referral is indicated.

Case 1 Your Answer:

No Answer Submitted

Case 2

Case 2 Model Answer:

Eosinophilic granuloma

Findings and interpretation:


  • There is a lucent, expansile lesion in the tibial diaphysis, centred on the medulla, which shows a wide zone of transition. It is causing endosteal scalloping and significant cortical erosion and breach.
  • There is a thick, dense and solid appearing periosteal reaction at the tibial diaphysis.


  • There is a soft tissue mass in the tibial diaphysis, showing high STIR and iso-intense T1 signal intensity.
  • There is significant surrounding high STIR and T2 fatsat signal which extends into the adjacent bone marrow of the tibia and periosteum as well as the surrounding soft tissues, indicating oedema.
  • The mass breaks through the cortex to the surrounding soft tissues. It is avidly enhancing on the post contrast sequences.

Pertinent negative findings:

  • There is no pathological fracture.
  • No abscesses / sinus tracts on MRI.

The findings represent a moderately aggressive bony lesion; the solid periosteal reaction implies chronicity and healing.


Principal diagnosis:

Eosinophilic granuloma.


Differential diagnosis:

  • Ewing’s sarcoma
  • Osteomyelitis
  • Bony metastasis



Alert referring physician of findings.

Recommend bone scan to search for multiple bone involvement.

Recommend discussion at paediatric orthopaedic MDT regarding image guided biopsy for histopathological diagnosis.

Case 2 Your Answer:

No Answer Submitted

Case 3

Case 3 Model Answer:

Re-activation pulmonary tuberculosis complicated by mycotic aneurysm

Findings and interpretation:

  • There are widespread centrilobular nodules occupying large portions of both lungs, showing a predilection for the upper lobes, right middle lobe and lingula. The lung bases are relatively spared.
  • There are multiple cavities of varying size, showing thick, irregular walls. These are located in both upper lobes and the apical segment of the right lower lobe.
  • There is subsegmental consolidation in the right middle lobe.
  • There is a cluster of nodules in the left lower lobe which show a ground glass halo.
  • There is pneumomediastinum.
  • On the post contrast images, there is a saccular structure at the wall of the largest cavity in the right upper lobe which fills with contrast. This does not appear continuous with any of the visualised pulmonary arteries.

Pertinent negative findings:

  • No significantly enlarged mediastinal / cervical lymph nodes.
  • No involvement of the spine / visualised bones.


The findings represent manifestations of an infectious disease in the lungs, with active endobronchial spread. Ground glass halos around the nodules represent alveolar haemorrhage. The contrast filled structure represents a pseudo-aneurysm, caused by damage to an adjacent bronchial arterial branch by the infectious process.


Principal Diagnosis:

Re-activation cavitating pulmonary tuberculosis complicated by mycotic pseudo-aneurysm formation.


Differential diagnosis:

  • Rasmussen aneurysm originating from a pulmonary artery.
  • Cavitating pneumonia caused by a different organism such as aspergillus or cryptococcosis.



  • Urgently contact referring physician and inform of findings.
  • Recommend interventional radiology opinion with regards to endovascular management of the pseudo-aneurysm.
  • Correlate with sputum cultures for acid-fast bacilli. The patient should be isolated and close contacts screened for disease.

Case 3 Your Answer:

No Answer Submitted

Case 4

Case 4 Model Answer:

Small bowel volvulus causing closed loop obstruction

Findings and interpretation:

  • The small bowel is dilated down to a segment of ileum, where a transition point is noted. The transition point leads to a cluster of dilated loops in the lower central abdomen which show a radial configuration (seen best on coronal sequence). Past this cluster of loops the small bowel is collapsed.
  • The two transition points of collapsed bowel which lead to the cluster of dilated loops are adjacent to one another, demonstrating the ‘double beak sign’ which indicates tapered bowel at two points of obstruction.
  • The clustered loops located in the pelvis show thickened and oedematous walls, which also demonstrate very little enhancement compared to the remainder of the small bowel.
  • There is peri-hepatic and peri-splenic, as well as pelvic free fluid.
  • There is a subcutaneous soft tissue mass in the lower anterior chest.

Pertinent negative findings:

  • There is no pneumatosis intestinalis / portal venous gas.
  • No extra-luminal air to suggest perforation.

Incidental findings:

  • Small umbilical hernia containing omental fat
  • Calcified uterine fibroids


The findings represent small bowel obstruction caused by a closed loop obstruction, complicated by strangulated small bowel loops, with impending ischemia. 


Principal diagnosis:

Closed loop obstruction secondary to small bowel volvulus.


Differential diagnosis:

  • Internal hernia with strangulated bowel loops.
  • Small bowel obstruction caused by adhesions: this is unlikely as it does not usually cause two points of obstruction.



Urgently contact referring physician and inform of findings. A nasogastric tube must be placed immediately. These cases are usually managed by emergent laparotomy.

The incidentally found soft tissue mass in the chest wall requires follow up with ultrasound and possible biopsy.

Case 4 Your Answer:

No Answer Submitted

Case 5

Case 5 Model Answer:

Mesenteric panniculitis with portal vein thrombosis


28 year old man with abdominal pain.


CT abdomen and pelvis portal venous phase


Findings and interpretation:

  • There is an area of mesenteric fat stranding at the root of the small bowel mesentery, with a thin surrounding capsule. This area surrounds the superior mesenteric vessels at their origin.
  • There are multiple enlarged lymph nodes within the area of fat stranding. Enlarged lymph nodes are also detected within the small bowel mesentery more distally.
  • There are also enlarged coeliac, porta hepatis, para-aortic and aorto-caval lymph nodes.
  • There is no enhancement / contrast filling of the portal vein, splenic vein or superior mesenteric vein.

Pertinent negative findings:

  • There is no evidence of fibrosis or calcification
  • There is no evidence of associated abdomino-pelvic malignancy.


The findings represent a non-specific, likely inflammatory process involving the small bowel mesentery and retroperitoneal area. This is causing secondary thrombosis of the portal, splenic and superior mesenteric veins.


Principal diagnosis:

Mesenteric panniculitis complicated by portal vein thrombosis.


Differential diagnosis:

  • Lymphoma
  • Metastatic spread of unidentified malignancy



Urgently alert referring physician of acute portal vein thrombosis to start treatment immediately.

Recommend discussion at gastro-intestinal MDT and image guided biopsy of one of the lymph nodes.

Recommend periodic follow up imaging, as this condition may develop into lymphoma.

Case 5 Your Answer:

No Answer Submitted

Case 6

Case 6 Model Answer:

Oto-mastoiditis with intracranial spread causing meningo-encephalitis

Findings and interpretation:


  • There is complete soft tissue opacification of the right mastoid air cells, as well as partial opacification of the middle ear cavity.
  • There is an extra-axial, midline soft tissue mass lying within the anterior cranial fossa.


  • There is cortical FLAIR and T2 hyperintensity which involves the right cerebral hemisphere, mostly at the parietal, occipital, temporal and insular regions, and is also seen within the occipital horns of the lateral ventricles.  
  • There is pachymeningeal enhancement on the post contrast sequences which involves both hemispheres but is greater on the right side. There is marked leptomeningeal enhancement at the right cerebral hemisphere.
  • There is high T2 signal within the mastoid air cells on the right side, as well as avid mucosal enhancement of the mucosal lining and post-contrast enhancement of the mastoid bone, extending to the roof of the mastoid air cells and the skull base.
  • Scattered high DWI signal with corresponding low ADC values is detected at both cerebral hemispheres, most prominent at the right parietal and occipital cortices, along both insular cortices, and in a dependent position within both lateral ventricles.  High DWI signal is also seen at the right mastoid air cells. This indicates diffusion restriction.
  • The previously mentioned midline extra-axial soft tissue mass shows iso-intense T2 and T1 signal, is homogeneous, and shows homogeneous and avid post-contrast enhancement.

Pertinent negative findings:

  • There is no sigmoid sinus thrombosis.
  • There are no brain abscesses.


The findings represent acute infection of the right mastoid and middle ear, which has spread locally through the tegmen into the contents of the cranial vault, causing infection of the meninges, ventricles and cerebral hemispheres. The extra-axial mass has a benign, non-aggressive appearance and is incidentally found in this case.


Principal diagnosis:

Right oto-mastoiditis with intracranial spread causing meningo-encephalitis and incidental meningioma.


Differential diagnosis:

  • Sarcoid thickening of the meninges with unrelated fluid in the mastoid air cells (however, this would have a different appearance with nodular thickening and would not show diffusion restriction).  
  • Meningeal metastases (this is also much less likely because nodular thickening would be seen).



Urgently contact referring physician and inform of findings.

Recommend urgent neurological referral.

Case 6 Your Answer:

No Answer Submitted
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